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Suggested Citation:"Appendix C: Poster Abstracts." National Research Council. 2008. Bioinspired Chemistry for Energy: A Workshop Summary to the Chemical Sciences Roundtable. Washington, DC: The National Academies Press. doi: 10.17226/12068.
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Suggested Citation:"Appendix C: Poster Abstracts." National Research Council. 2008. Bioinspired Chemistry for Energy: A Workshop Summary to the Chemical Sciences Roundtable. Washington, DC: The National Academies Press. doi: 10.17226/12068.
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Suggested Citation:"Appendix C: Poster Abstracts." National Research Council. 2008. Bioinspired Chemistry for Energy: A Workshop Summary to the Chemical Sciences Roundtable. Washington, DC: The National Academies Press. doi: 10.17226/12068.
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Suggested Citation:"Appendix C: Poster Abstracts." National Research Council. 2008. Bioinspired Chemistry for Energy: A Workshop Summary to the Chemical Sciences Roundtable. Washington, DC: The National Academies Press. doi: 10.17226/12068.
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Suggested Citation:"Appendix C: Poster Abstracts." National Research Council. 2008. Bioinspired Chemistry for Energy: A Workshop Summary to the Chemical Sciences Roundtable. Washington, DC: The National Academies Press. doi: 10.17226/12068.
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Suggested Citation:"Appendix C: Poster Abstracts." National Research Council. 2008. Bioinspired Chemistry for Energy: A Workshop Summary to the Chemical Sciences Roundtable. Washington, DC: The National Academies Press. doi: 10.17226/12068.
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Suggested Citation:"Appendix C: Poster Abstracts." National Research Council. 2008. Bioinspired Chemistry for Energy: A Workshop Summary to the Chemical Sciences Roundtable. Washington, DC: The National Academies Press. doi: 10.17226/12068.
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Suggested Citation:"Appendix C: Poster Abstracts." National Research Council. 2008. Bioinspired Chemistry for Energy: A Workshop Summary to the Chemical Sciences Roundtable. Washington, DC: The National Academies Press. doi: 10.17226/12068.
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Appendix C Poster Abstracts Artificial Hydrogenase SystemS [FeFe]hydrogenase. This is a rare example of FeIFeII para- magnetic H2ase model complex studied by X-ray diffraction. Redox Reactivity of Amine Hydrides of Iridium As compared with complex D, a remarkable reorientation of Zachariah M. Heiden and Thomas B. Rauchfuss the IMes NHC ligand enables the (μ-pdt)[Fe(CO)2(PMe3)] Department of Chemistry, University of Illinois, Urbana, [Fe(CO)2(IMes)]+ cation, Dox, to exist as a “rotated” struc- IL 61801 ture, with structural and spectroscopic similarities to the diiron unit of Has isolated or Hox (Nicolet et al., 200; Roseboom Metal hydrido-amine complexes (metal = Ru, Rh, et al., 2006). The structural makeup of the model includes and Ir) popularlized by Noyori et al. are highly active and a Fe-Fe distance that matches that of the enzyme, a semi­ e ­ nantioselective transfer hydrogenation catalysts. Much of bridging CO group, and a pseudo-octahedral iron with open their reactivity beyond use as transfer hydrogenation cata- site blocked by a strategically positioned arene group from lysts remains relatively unexplored. The metal diamido com- the bulky NHC carbene ligand (Peters et al., 1998; Nicolet et plexes behave as a dehydrogenase-related catalyst toward al., 1999). Other asymmetric disubstituted diiron complexes, alcohol/organic substrates. We have found that protonation (μ-pdt)[FeI(CO)2(P)][FeI(CO)2L)] with a selection of P-donor of the unsaturated diamido derivatives affords an unusual and NHC ligands designed to illustrate the principles that class of soft Lewis acids that will be described. Furthermore, govern stability and function of the FeIFeII redox level are the hydrido-amines act as an oxygenase, and homogeneous being studied. The reactivity of the mixed valent FeIFeII fuel cell, catalyzing the unusual reduction of dioxygen with species is being explored. ­ hydrogen similar to knall gas bacteria, resulting in water as the only byproduct. Mixed Valent, Fe(II)Fe(I), Diiron Complexes Reproduce the Unique Rotated State of the [FeFe]Hydrogenase Active Site Tianbiao Liu and Marcetta Y. Darensbourg Department of Chemistry, Texas A&M University, College Station, TX 77843 A-1.eps (1) Nicolet, Y. L., B. J. Lemon, J. C. image bitmap Fontecilla-Camps, and J. W. Peters. The reversible Fe Fe D Fe Fe couple of an N- I I I II Trends Biochem. Sci. 2000, 25, 138-143. h ­ eterocyclic carbene dinuclear FeIFeI complex, (μ-pdt) (2) ����������������������������������������������������������������������� Roseboom, W. D. L., A. L. De Lacey, V. M. Fernandez, E. C. Hatchikian, [FeI(CO)2(PMe3)][FeI(CO)2(IMes)] (IMes= 1,3-bis(2,4,6- and S. P. J. Albracht, J. Biol. Inorg. Chem. 2006, 11, 102–118. (3) ������������������������������������������������������������������ Science Peters, J. W., W. N. Lanzilotta, B. J. Lemon, and L. C. Seefeldt, trimethylphenyl)imidazol-2-ylidene), complex D, has led to 1998, 282, 1853 –1858. the isolation of the mixed-valent cationic complex Dox as a (4) ������������������������������������������������������������������������� Nicolet Y., C. Piras, P. Legrand, C. E. Hatchikian, and J. C. Fontecilla- biomimetic of the 2Fe2S subsite of the oxidized H cluster in Camps, Structure 1999, 7, 13– 23. 45

46 APPENDIX C Toward Understanding the Way Hydrogen Is Formed Biomimetic Efficiency: A Structural and Electronic and Consumed at the Catalytic Center in the Ni-Fe Investigation of Rotational Barriers Found in DFT- Hydrogenase Enzymes inspired Fe-hydrogenase Models Michelle Millar, Dao Nguyen, Harmony Voorhies, and Susan Michael Singleton, Roxanne Jenkins, and Marcetta Y. Beatty, Department of Chemistry, SUNY Stony Brook, Stony Darensbourg Brook, New York 11794-3400 Department of Chemistry, Texas A&M University, College Station, TX 77843 The Ni-Fe containing hydrogenases are multi­component enzymes that catalyze the reversible production and con- While the literature is filled with structural models of sumption of H2. Beyond the biological significance, these Fe-hydrogenases, a truly efficient functional model for the enzymes have been heralded as models for potentially uptake or production of hydrogen gas has yet to be realized. low-cost, efficient electrode replacements for the unique Pt This deficiency is often blamed on the fact that most struc- electrode systems in fuel cells. We have acquired a number tural models do not contain the unique “rotated” or entatic of special nickel-thiolate compounds that replicate some state that is the consensus structure of the enzyme active site of the unusual structural and electronic and redox proper- (eas) in its resting state.1 As demonstrated by 13C VT NMR ties of the Ni center in hydrogenases, including series of studies the minimal model of the eas, (µ-pdt)[FeI(CO)3]2 Ni(II), NI(III) and Ni(IV) redox levels, Ni-H and Ni-CO shows mobility in the FeI(CO)3 units via apical/basal intra- i ­nteractions, as well as Ni-Fe compounds that replicate a por- molecular CO exchange and in the 3-atom S to S linker.2 tion of the Ni-Fe centers in hydrogenase. Attempts to acquire Density functional theory computations have suggested species that display electrocatalysis will be presented. The that an electronic effect engendered by the substitution of ligands ­developed for this chemistry contain the PS3 and PS2 a CO by a better donor ligand, (µ‑pdt)[FeI(CO)3][FeI(CO c ­ oordinating entities, as well as related derivatives. )2L], lowers the barrier to rotation of the nonsubstituted Fe(CO)3 unit.3 The computations also suggest that a steric effect in the µ-SRS bridge promotes rotation. In an effort New Concepts in Hydrogen Processing: Modeling the to verify the computational results, we have prepared a Hmd Cofactor and Redox Active Ligands with Platinum series of ­ sterically bulky (µ-SRS)[Fe(CO)3]2 complexes Metals such as the (µ‑SCH2C(Me)2CH2S)[FeI(CO)3]2 shown left Aaron Royer, Swarna Kokatam, Zachariah Heiden, Thomas and characterized them by various X-ray diffraction as B. Rauchfuss well as other ­ spectroscopies, including 13C VT NMR. The prospective application of functional biomimetic models The enzyme H 2 -forming methylenetetrahydro­ toward the development of cost-effective fuel cells has methanopterin dehydrogenase, Hmd, is associated with also led to the evaluation of the all CO compounds as well a central step in methanogenesis by Ni-starved archaea. as the L-­substituted derivatives as electrocatalysts for H2 The active site contains an Fe(II) bound organic 3,5- production. d ­ imethylpyrid-2-one-6-acetic acid group conjugated to a nucleotide. While the Fe complexation in the native enzyme (1) Nicolet, Y. L., B. J. Lemon, J. C. Fontecilla-Camps, and J. W. Peters. Trends Biochem. Sci. 2000, 25, 138-143. is yet unknown, we have examined the coordination and (2) Lyon, E. J., I. P. Georgakaki, J. H. Reibenspies, and M. Y. Darensbourg, r ­ eactivity of a similar organic ligand, 6-carboxymethyl-4- J. Am. Chem. Soc. 2001, 123, 3268-3278. methyl-2-hydroxypyridine, with Cp*Rh(III). In order to (3) Tye, J. W., M. Y. Darensbourg, and M. B. Hall, Inorg. Chem. 2006, 45, probe the role of the co­factor, de­hydrogenation of second- 1552-1559. ary alcohols and interligand hydrogen bonding will be discussed. Transition metal ions with organic radicals exist in the active sites of metalloproteins. The best understood example is galactose oxidase, which features a single Cu(II) ion coor- dinated to a modified tyrosyl radical. Many combined experi- mental and theoretical studies have focused on electronic properties of metal complexes with redox active ligands, yet reactivity beyond characterization has been limited. We will demonstrate the influence of the metal complex redox state on H2 activation by anilino-phenolate noninnocent ligands.

APPENDIX C 47 Previous lower-frequency electron spin echo envelope Cys S modulation (ESEEM) studies showed a histidine nitrogen S S [4Fe4S] interaction with the Mn cluster in the S2 state, but the Fe Fe OC C amplitude and resolution of the spectra were relatively poor N C C C N Hδ+ at these low frequencies. With the intermediate frequency δ+ O O H instruments we are much closer to the “exact cancellation” enzyme active site limit, which optimizes ESEEM spectra for hyperfine-coupled “entatic” state nuclei such as 14N and 15N. We will report the results on 14 N and 15N labeled PSII at these two frequencies, along with simulations constrained by both isotope datasets at both ­ frequencies, with a focus on high-resolution spectral S S CO determination of the histidine ligation to the cluster in the Fe Fe S2 state. OC C OC C C O O O transition state Photochemical Production of Hydride Donor with structure of mode R ­ uthenium Complexes with an NAD+ Model Ligand Etsuko Fujita,1 Dmitry Polyansky,1 Diane Cabelli,1 Koji Tanaka,2 and James T. Muckerman1 1 Chemistry Department, Brookhaven National Laboratory, Upton, NY 11973-5000, USA OC S O 2 Institute for Molecular Science and CREST, 5-1 Higashiyama, ­Myodaiji, S C Okazaki, Aichi 444-8787, Japan Fe Fe OC CO OC CO NAD+/NADH is one of the most important redox ground state mediators in biological systems, including photosystem I, structure of mode and acts as a reservoir/source of two electrons and a proton. A polypyridylruthenium complex with an NAD+ functional A-2.eps model ligand investigated here is the first example that an NAD+/NADH model complex works as a catalytic hydride donor for chemical reactions such as the electroreduction of acetone to 2-propanol (Koizumi and Tanaka, 2005). Herein we report clear evidence (Polyanski et al., in press) of photo­ chemical formation of a hydride donor that can transfer a hydride or its equivalent to acetone, and ultimately to C1 species derived from CO2 reduction as nature does. These results open a new door for photocatalytic hydride (or p ­ roton-coupled-electron) transfer reactions originating from A-3.eps metal-to-ligand charge-transfer (MLCT) excited states of metal complexes with a bioinspired NADH-like ligand, and bitmap image—enlarged only 110% to preserve resolution to a new path for generating fuels from solar energy. point The research carried out at Brookhaven National Labo- Artificial Photosynthetic Systems ratory was supported under contract DEAC02-98CH10886 with the U.S. Department of Energy. Multifrequency Pulsed EPR Studies of the Manganese Cluster of PSII (1) Koizumi, T., and K. Tanaka, Angew. Chem. Int. Ed. 2005, 44, Greg Yeagle, Richard Debus, R. David Britt 5891-5894. (2) Polyansky, D., D. Cabelli, J. T. Muckerman, E. Fujita, T. Koizumi, T. Fukushima, T. Wada, and K. Tanaka, Angew. Chem. Int. Ed. 2007, We are completing the construction of our CalEPR in press. center at UC-Davis (http://brittepr.ucdavis.edu) with five research-grade EPR instruments. Of particular note here are two pulsed EPR instruments working at the intermediate microwave frequencies of 31 and 35 GHz that are provid- ing new high-resolution data on amino acid coordination of the important water-splitting manganese cluster of Photo­ system II (PSII).

48 APPENDIX C Pathway to the Artificial Photosynthetic Unit lifetimes of energy hopping between chromophores in each Elias Greenbaum,1 Barbara R. Evans,1 Hugh M. O’Neill,1 array were determined using femtosecond transient absorp- and Ida Lee2 tion spectroscopy. Solution-phase electron paramagnetic 1 Chemical Sciences Division, Oak Ridge National Laboratory resonance (EPR) and electron-nuclear double resonance 2 Department of Electrical Engineering, University of Tennessee (ENDOR) studies on chemically oxidized arrays reveal that an unpaired electron is shared between the redox centers in A key objective in the field of bioinspired chemistry the covalent arrays on a timescale faster than 107 Hz. Future for energy production is a comprehensive understanding of work involves characterization of charge migration in the light-driven electron transfer and the generation of a ­rational noncovalently assembled systems. model to serve as a template for future synthetic nano­ materials for solar fuels production. Research at Oak Ridge National Laboratory is aimed at integration of fundamental Bioinspired Supramolecular Device and Self-Assembly m ­ olecular structural, kinetic, and mechanistic understand- for Artificial Photosynthetic Reaction Center ing of the conversion of solar energy into chemical energy. Oh-Kil Kim,1 Mike Pepitone,1 Sungjae Chung,1 Joseph The critical science problems of this area of research are the Melinger,2 Glenn Jernigan,2 and Daniel Lowry3 harvesting of solar photons throughout the visible region of 1 Chemistry Division. the solar emission spectrum and the photocatalytic forma- 2 Electronics Science & Technology Division. tion of small fuel molecules, such as hydrogen, methanol, 3 Center for Biomolecular Science & Engineering, and Institute for Nanoscience or methane. Using natural photosynthesis as our inspiration combined with biological-synthetic (“soft-hard”) catalyst structures, we will couple biomimetic light-activated ener- A unique supramolecular device is architectured for getic reactions to nanoscale photocatalytic chemistry to artificial photosynthetic reaction center based on helical drive the fuel-forming reactions and use water as the source amylose, which is a linear chain polymer of 1,4-α D-glucose of electrons. This research program will produce the first and capable of encapsulating various guest molecules as artificial photosynthetic units and artificial photosynthetic long as the size and interaction forces are compatible with membranes. Success in this area will have a significant each other. A photo/electro-active donor-acceptor (D-A) pair impact on the larger picture of a fossil-fuel-free future in chromophore is included and rigidified inside the helix, and which renewable fuels are produced by bioinspired photo- the helical surface is templated by an array of cyanine dye catalytic systems. J-aggregates (super-helix). Such integration of the supra- molecular entity occurs by spontaneous self-­organization processes in the presence of amylose and the resulting Linker Controlled Energy and Charge Sharing Chloro- nanodevice becomes water soluble. phyll A Assemblies A close photonic/electronic communication takes place Richard F. Kelley,1 Michael J. Tauber,2 and Michael R. across the helix between the J-aggregates (antenna) and Wasielewski1 the chromophore (inside the helix) such that very efficient 1 Department of Chemistry, Northwestern University, 2145 Sheridan exciton/electron-transfer proceeds unidirectionally along Road, Evanston, IL 60208 the helical axis. Energy-transfer (ET) and electron-transfer 2 Department of Chemistry and Biochemistry, University of California, (eT) from the antenna to D, and from D to A in the confined San Diego, CA 92093 chromophore, respectively, were investigated based on fluo- rescence quenching and excited-state lifetime measurements The ability of chlorophyll molecules to act as donors and with respect to the helical encapsulation, D-A distance, acceptors for both energy and charge transfer in natural pho- D/A strength. A remarkably efficient (> 95 percent) ET and tosynthetic systems makes the incorporation of these chro- eT over D-A distance >20 Å were observed with distinct mophore/redox centers into artificial photosystems highly distance dependence and directionality for the encapsulated desirable. Here we present the first Suzuki and Sonogashira chromophores in clear contrast with the encapsulation-free cross-coupling to the 20-meso position of chlorophyll a. This counterparts. It was also found that the helical encapsulation methodology was used to rigidly incorporate chlorophyll a is a powerful means to develop a highly ordered self-­assembly molecules into several arrays using both covalent and non- of chromophores onto a substrate. This was proved by a fast covalent interactions. The rigid linkers allow efficient energy redox reaction in cyclic voltammetry and oriented thin films transfer among neighboring chlorophylls, efficient charge often as helical bundles (AFM) upon casting ­aqueous solu- transfer between chlorophylls in the covalent arrays, and tion. These were not observable with the encapsulation-free unhindered self-assembly of the arrays in nonpolar media. chromophores under the conditions employed. Small-angle X-ray scattering (SAXS) measurements using the high-flux synchrotron radiation of the Advanced Photon Source at Argonne National Laboratory was used to elucidate the structures of the noncovalent assemblies. The picosecond

APPENDIX C 49 Light Energy Conversion by Photosynthetic Proteins at for a wide range of oxidation reactions because Mn(III) is Inorganic Electrodes only well known as a stoichiometric oxidant. Our aim is to Nikolai Lebedev make the reaction catalytic. U.S. Naval Research Laboratory, 4555 Overlook Ave., Wash- ington, DC 20375 (1) “Water-Splitting Chemistry of Photosystem II”, James P. McEvoy and Gary W. Brudvig (2006) Chem���������� 4455-4483. . �������� Rev����� . 106, (2) “Quantum Mechanics/Molecular Mechanics Structural Models of the The photosynthetic reaction center (RC) is one of Oxygen-Evolving Complex of Photosystem II”, Eduardo M. Sproviero, the most advanced light-sensing and energy-converting José A. Gascón, James P. McEvoy, Gary W. Brudvig and Victor S. m ­ aterials developed by nature. Its coupling with inorganic Batista (2007) Curr. Opin. Struct. Biol. 17, 173-180. surfaces is attractive for the identification of the mecha- (3) “A Functional Model for O-O Bond Formation by the O2-Evolving Complex in Photosystem II”, Julian Limburg, John S. Vrettos, Louise nisms of interprotein electron transfer (ET) and for the M. Liable-Sands, Arnold L. Rheingold, Robert H. Crabtree and Gary possible applications for the construction of protein-based W. Brudvig (1999) Science 283, 1524-1527. innovative photoelectronic and photovoltaic devices. Using (4) “Speciation of the Catalytic Oxygen Evolution System: [MnIII/IV2(μ‑O)2 genetically engineered bacterial RC proteins and specifi- (terpy)2(H2O)2](NO3)3 + HSO5-”, Hongyu Chen, Ranitendranath Tagore, cally synthesized organic linkers, we were able to construct Gerard Olack, John S. Vrettos, Tsu-Chien Weng, James Penner-Hahn, Robert H. Crabtree and Gary W. Brudvig (2007) Inorg. Chem. 46, self-assembled and aligned biomolecular surfaces on vari- 34-46. ous electrodes, including gold, carbon, indium tin oxide (ITO), highly ordered ­ pyrrolytic graphite (HOPG), and carbon nanotube (CNT) arrays. Our results show that after Bioinspired Water Oxidation Catalysts for Renewable immobilization on the electrodes, the photosynthetic RC can Energy Production operate as a highly efficient photosensor, optical switch, and Greg A. N. Felton,1 Robin Brimblecombe,2 Johanna ­Scarino,1 photovoltaic device. John Sheats,3 Gerhard F. Swiegers,4 Leone Spiccia,2 G. Charles Dismukes.1 Water Oxidation 1 Department of Chemistry and the Environmental Institute, Princeton University. 2 School of Chemistry Monash University, Australia. Bioinspired Manganese Complexes for Solar Energy 3 Science Faculty, Rider University. 4 Division of Molecular Science Commonwealth Scientific and Industrial Utilization Research Organisation, Australia. Gary W. Brudvig, Sabas G. Abuabara, Clyde W. Cady, Jason B. Baxter, Charles A. Schmuttenmaer, Robert H. Crabtree, The capture of light energy to drive water splitting and Victor S. Batista is considered key to future renewable energy production. Department of Chemistry, Yale University, PO Box 208107, Studies of the natural photosynthetic water oxidation com- New Haven, CT 06520-8107 plex (WOC) of photosystem II (PSII) have led to a series of bioinspired model compounds. These compounds contain Manganese complexes that catalyze the evolution of [Mn4O4]7+ cubic cores. Presently, conditions have been oxygen from water, inspired by the oxygen-evolving complex discovered that enable these manganese-oxo cubanes to of photosystem II (McEvoy and Brudvig, 2006; Spoviero. et catalyze the sustained photo-assisted oxidation of water, for al., 2007), have been extensively investigated by our group several thousand turnovers. These conditions are based on (Limburg et al., 1999; Chen et al., 2007). With the goal of the doping of these cubane compounds into a Nafion® film. using water-oxidation catalysts for solar energy utilization, The properties of these compounds, along with the nature of we have studied the photochemistry of TiO2 nanoparticles the conditions use in their incorporation into photoanodes, to which a Mn(II)‑terpy complex is covalently attached are being vigorously explored. (terpy = 2,2′:6,2″-terpyridine). These TiO2 nano­particles exhibit visible-light sensitization and charge separation as evidenced by UV-visible, terahertz, and EPR spectroscopy Fine-Tuning the Redox Potential of Mn4O4L6 Cubes by of colloidal thin films and aqueous suspensions. Photoexcita- Use of Substituted Diarylphosphinic Acids tion of [MnII(H2O)3(catechol-terpy)]2+/TiO2 surface-attached John E. Sheats,1 G. Charles Dismukes,2 Paul Lucuski,1 complex leads to Mn(II)→Mn(III) photooxidation within M ­ arlena Konieczynska,1,3 Eric Sellitto,1,4 Esteban Alverado, 1,3 300 fs, as indicated by terahertz spectroscopic measurements Matthew Vecchione,1,4 and Arren Washington1,4 and computational simulations of interfacial electron trans- 1 Department of Chemistry, Biochemistry, and Physics, Rider University, fer. The half-time for regeneration of the Mn(II) complex is Lawrenceville, NJ 08648. ca. 23 sec (at 6 K), as monitored by time-resolved measure- 2 Department of Chemistry, Princeton University, Princeton, NJ 08544. ments of the Mn(II) EPR signal. These results are expected 3 Project SEED Student 4 Undergraduate Student, Rider University. to be particularly relevant to photocatalytic applications of Mn(III) complexes, which are known to be effective catalysts

50 APPENDIX C Dismukes and coworkers have demonstrated that ciency of photovoltaic devices. Surface texturing has become Mn4O4L6 (L=Ar2PO2-), when bound to a Nafion-coated elec- a common practice for Si solar cells and, in combination with trode, can oxidize H2O to produce H2 and O2 in a catalytic vacuum deposited antireflection coatings (ARCs), reduces cycle for up to 50,000 turnovers. The voltage required is reflection losses a few percent. Unfortunately, the high 1.20 V, the same as needed for photosynthetic oxygen evo- cost of vacuum deposition of ARCs is a big challenge for lution. The Mn cubes have been isolated in four oxidation economic production of large photovoltaic panels. Inspired states: Mn4 (III) 4O2(OCH3)2L6 to Mn4(III)(IV)3O4L6+. The by the antireflection properties of moth eyes, we have devel- redox potential for the oxidation of Mn4O4L6 (L=(C6H5)2PO2) oped subwavelength ARCs for crystalline silicon solar cells. to Mn4O4L6+, 1.20 V, can be reduced by 0.15 V by using Wafer-scale, crystalline arrays of inverted pyramids, which (4–CH3O–C6H4)2PO2– and increased substantially by use directly function as efficient ARCs, are anisotropically of (3–NO2–C6H4)2PO2–. Experiments are underway to test etched in silicon substrates by a cheap yet scalable non- stronger electron donors such as 4 –(CH 3) 2N –C 6H 4 and lithographic technique. The inverted pyramid array on Si 4–t–C4H9O–C6H4 and weaker acceptors such as 4–CF3-C6H4 dramatically reduces the specular reflectivity of the surface and 3 –Cl –C 6H 4. Methods for covalently anchoring the and consequently has the potential to increase the conversion Mn cubes to the surface of an electrode are also being efficiency of silicon solar cells. investigated. X-ray Fingerprinting Bioinspired Supramolecular Struc- Solar Cells ture and Dynamics in Solution Self-Assembled Biomimetic Multifunctional Coatings D. M. Tiede,1 X. Zuo,1 L. X. Chen,1 and K. Attenkofer2 Nicholas C. Linn, Chih-Hung Sun, Peng Jiang 1 Chemistry Division and 2Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, 60439 Department of Chemical Engineering, University of Florida, Gainesville, FL 32611 Bioinspired, self-assembling supramolecular materials We report a simple bioinspired self-assembly technique are increasingly being designed for applications in solar for fabricating multifunctional optical coatings that mimic energy conversion and storage. However, the dynamic fea- both unique functionalities of antireflective motheye and tures of these molecular materials typically preclude struc- superhydrophobic cicada wing. Wafer-scale, non-close- tural analyses using crystallographic techniques. This makes packed colloidal crystals with remarkably large hexagonal in situ structural characterization a critical challenge. We domains are created by a spin-coating technology, which have developed techniques that combine wide-angle solution is based on shear-aligning colloidal silica particles sus- X-ray scattering (WAXS) measured to better than 2 Å spatial pended in nonvolatile triacrylate monomers. The resulting resolution with atomistic simulation to provide a new experi- polymer-embedded colloidal crystals exhibit highly ordered mental approach for the characterization of supramolecular surface modulation and can be used directly as templates to solution state structure. Comparisons between experimental cast poly(dimethylsiloxane) (PDMS) molds. Moth-eye anti­ scattering patterns measured for a range of proteins, DNA, reflection coatings with adjustable reflectivity can then be metal coordination complexes, and host-guest assemblies molded against the PDMS master. The specular reflection show WAXS and corresponding pair distribution function of replicated nipple arrays matches the theoretical prediction (PDF) patterns to be sensitive to supramolecular conforma- using a thin-film multilayer model. The microstructures of tion, dynamics, and solvation. For example, a comparison of the replicated films also lead to the formation of hydrophobic experimental scattering and PDF patterns for γ-cyclodextrin surfaces, even though the native material is inherently hydro- show features characteristic of the host structure, configura- philic. These biomimetic materials are of great technological tional broadening, and solvation. In current work we are test- importance in developing self-cleaning antireflection optical ing the ability of WAXS to serve as a benchmark for quan- coatings for crystalline silicon solar cells. titative evaluation of molecular dynamics simulations. The ability to provide an experimental marker for supra­molecular dynamics and solvation that is directly connected to coor- Nanopyramid Arrays for Solar Cells dinate models represents a new opportunity for resolving Chih-Hung Sun, Nicholas C. Linn, Peng Jiang structural dynamics coupled to light-induced charge separa- Department of Chemical Engineering, University of Florida, tion in natural and artificial host matrices. Toward this end we Gainesville, FL 32611 are extending the WAXS technique to include pump-probe techniques at the Advanced Photon Source. Future work is Current production of solar cells is dominated by crys- planned for combining 100 ps time-resolved WAXS, X-ray talline silicon modules; however, due to the high refractive spectroscopy, and magnetic resonance data to achieve a more index of silicon, more than 30 percent of incident light is complete picture of structural reorganization resolved during reflected back, which greatly reduces the conversion effi- the time-course of solar energy conversion function.

APPENDIX C 51 suited for nanomaterials research. This bioinspired material has many unique properties that bridge the gap between pro- teins and bulk polymers. Like proteins, they are a sequence- specific heteropolymer, capable of folding into specific shapes and exhibiting potent biological activities; and like polymers, they are chemically and biologically stable and relatively cheap to make. Peptoids are efficiently assembled via automated solid-phase synthesis from hundreds of chemi- cally diverse building blocks, allowing the rapid generation of huge combinatorial libraries. This provides a platform to discover nanostructured materials capable of protein-like for γ-cyclodextrin with 1.0 Å spatial Experimental PDF measured A-4.eps molecular recognition and function. resolution (top) compared toonly 110% to preserve resolution bitmap image—enlarged PDF calculated from a coordinate model with resolution varying from 6 Å (1) to 0.4 Å (7). R2 R4 O O Biological Transformations N N OH HN N N Electrobiocatalytic Reduction of CO2 to Formate: Whole O O O Cell and Isolated Enzyme Systems R1 R3 R5 Boonchai Boonyaratanakornkit,1 Rolf J. Mehlhorn,1 Robert Peptoid Oligomer Kostecki,1 Douglas S. Clark1,2 1 Environmental Energy Technologies Division, Lawrence Berkeley A-5.eps N ­ ational Laboratory, Berkeley, CA 94720 enlarged only 110% for consistency 2 Department of Chemical Engineering, University of California, B ­ erkeley, CA 94720 Enzymatic reduction of CO2 to formate and ultimately to methanol can occur via concurrent electrochemical regen- eration of reduced cofactors. By using photovoltaic energy this bioelectrochemical reduction can provide transportable, energy-dense, carbon-neutral liquid fuels. The enzymes involved in fuel production are formate dehydrogenase (FDH) and methanol dehydrogenase, which use the co­factors methyl viologen and pyrroloquinoline quinine (PQQ), respectively. Two issues addressed are the O2-lability of FDH and electron transfer to the enzyme’s redox center. Whole- cell biocatalysis is explored by demonstrating that reduced cofactor is permeable to the cell membrane. Cells provide an intracellular environment that stabilizes FDH against O2 inactivation. Furthermore, we are connecting FDH to a graphite electrode via a PQQ-FAD linker to enable direct electron transfer from the electrode to the enzyme. This will obviate diffusion of cofactor into the enzyme’s redox center and should increase the rate of CO2 reduction. Bioinspired Polymers Bioinspired Polymers for Nanoscience Research Ronald Zuckermann Lead Scientist, Biological Nanostructures Facility The Molecular Foundry, Lawrence Berkeley National L ­ aboratory, Berkeley, California Peptoids are a novel class of non-natural biopolymer based on an N-substituted glycine backbone that are ideally

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Faced with the steady rise in energy costs, dwindling fossil fuel supplies, and the need to maintain a healthy environment - exploration of alternative energy sources is essential for meeting energy needs. Biological systems employ a variety of efficient ways to collect, store, use, and produce energy. By understanding the basic processes of biological models, scientists may be able to create systems that mimic biomolecules and produce energy in an efficient and cost effective manner. On May 14-15, 2007 a group of chemists, chemical engineers, and others from academia, government, and industry participated in a workshop sponsored by the Chemical Sciences Roundtable to explore how bioinspired chemistry can help solve some of the important energy issues the world faces today. The workshop featured presentations and discussions on the current energy challenges and how to address them, with emphasis on both the fundamental aspects and the robust implementation of bioinspired chemistry for energy.

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